The general objective of this research is to study the role of insulin in the synthesis and degradation of specific enzymes in rat tissues. The specific objective of this work is to study the role of insulin, other hormones (e.g., thyroxine, corticosterone, and growth hormone), and metabolites (e.g., glucose and fructose) in the control of the turnover of glucose-6-phosphate dehydrogenase in rat adipose tissue and liver. Prolonged incubation of epididymal adipose tissue, the in situ perfusion of rat liver, and incubation of isolated liver cells will be used in these studies in an effort to provide more rigorous control of experimental factors than is possible in the whole animal. The use of in vitro techniques in these experiments allows for the elucidation of the variables that are pertinent to the turnover of G6PDH without invoking responses from the whole-body homeostatic mechanisms.